DIGITAL NOTES ON Mobile Application Development B.TECH

Keep Content to a Minimum Don’t overwhelm your users – respect the small screen space. Keep content to a minimum.Make sure that content is universally supported on all devices or avoid it. Think Flash and then don’tuse it, for example.Make page descriptions short and to the point – for relevant bookmarks.Reduce the Inputs Required from Users Keep URLs short.Offering alternative input mechanisms (video, voice, etc.)Minimizing inputs in forms (you can always ask for more data when the user logs on to the desktop)Allowing permanent sign in (most smart phones are password or fingerprint protected – the risks ofstaying logged in are less than on the desktop)Keep scrolling to a minimum and only allow scrolling in one directionRemember Mobile Connections Are Not StableMobile connections can be a colossal PITA in areas with patchy service. Try: Retaining data so that it’s not lost in a connection breakMinimizing page size for rapid loadingKilling off ad-networks, etc. on mobile sites which consume huge amounts of bandwidth and dataKeeping images to a minimum and reducing the size of those imagesReducing the numbers of embedded images to a minimum (speeding up load times)Mobile 2.0Mobile 2.0 refers to services that integrate the social web with the core aspects of mobility – personal, localized,always-on and ever-present. A range of sites are available for both so-called "smartphones" and for moreordinary "feature" mobile phones. Ex: Micro-blogging services - Jaiku, Twitter, Pownce, CellSpin; Openplatforms for sms services - Fortumo and Sepomo; Information providing and services - mobeedo.Mobile Web DevelopmentWorking with Code : For coding our markup, JavaScript, and CSS, we can use almost any web tool availableon the market, including Adobe Dreamweaver, Microsoft Visual Studio, Eclipse, Aptana Studio, and of courseany good text editor, such as Sublime Text, Textmate, WebStorm, or Notepad .Adobe Dreamweaver : Since the CS5.5 version, Dreamweaver has worked better with mobile markup andallows us to validate against mobile web standards. When we create a new document we can choose HTML5 asthe document type.Adobe Edge Tools : Adobe offers a group of tools under the name of Edge that help designers and developersto create HTML5 applications such as Edge Code, Edge Reflow, Edge Inspect, and Edge .Microsoft Visual Studio and WebMatrix : Microsoft IDEs have supported HTML5 syntax and IntelliSensesince version 2010 SP1. WebMatrix for mobile web development is available for free.Eclipse : To use Eclipse as our development environment, there are several plug-ins you can use to createmobile HTML5 apps. Aptana from Titanium, a free Eclipse-based IDE for HTML5 and mobile developmentcan be downloaded as a free version from Aptana’s website.Native Web IDEs : To target native web or hybrid apps, some platforms offer tools and IDEs that can be usedto develop, test, and build the final packages.Testing : Emulators are very useful and provide a simple, fast, and fairly accurate testing solution. If it doesn’twork in the emulator, it probably will not work on the real device.Mobile Application DevelopmentPage 3

Emulators and Simulators : An emulator is a piece of software that translates compiled code from an originalarchitecture to the platform where it is running. An emulator is a desktop application that emulates mobiledevice hardware and a mobile operating system, allowing us to test and debug our applications and see theworking. The browser, and even the operating system, is not aware that it is running on an emulator.A simulator is a less complex application that simulates some of the behavior of a device, but does not emulatehardware and does not work over the real operating system. A simulator may be created by the devicemanufacturer or by some other company offering a simulation environment for developers. In mobile browsing,there are simulators with pixel-level simulation, and others that neither create a skin over a typical desktopbrowser (such as Firefox, Chrome, or Safari) with real typography nor simulate these browsers’ renderingengines.For mobile web development, we will find emulators from Nokia, BlackBerry, Android, webOS, and WindowsPhone, and simulators from Apple for iOS (though only for Mac OS X). A multiple mobile browser simulator isavailable from Adobe, called Device Central.Small Computing Device RequirementsThere are minimum resource requirements for a small computing device to run a J2ME application. First thedevice must have a minimum of 96 54 pixel display that can handle bitmapped graphics and have a way forusers to input information, such as a keypad, keyboard, or touch screen. At least 128 kilobytes (KB) ofnonvolatile memory is necessary to run Mobile Information Device (MID), and 8KB of nonvolatile memory isneeded for storage of persistent application data.To run JVM, 32KB of volatile memory must be available. The device must also provide two-way networkconnectivity. The native operating system must implement exception handling, process interrupts, be able to runthe JVM, and provide schedule capabilities. Furthermore, all user input to the operating system must beforwarded to the JVM, otherwise the device cannot run a J2ME application.J2ME OVERVIEW the Java development team enhanced the capabilities of Java to dramatically reduce the complexity ofdeveloping a multi-tier application. The team grouped features of Java into three editions, each having a software development kit (SDK). The original edition of Java, called the Java 2 Standard Edition (J2SE), consists of application programminginterfaces (APIs) needed to build a Java application or applet. The Java 2 Micro Edition (J2ME) contains the API used to create applications for small computing devices,including wireless Java applications. The development team at Sun worked on Java in the early 1990s to address the programming needs of thefledgling embedded computer market, but that effort was sidetracked by more compelling opportunitiespresented by the Internet. As those opportunities were addressed, a new breed of portable communications devices opened otheropportunities at the turn of the century. Cell phones expanded from voice communications devices to voice andtext communications devices. Pocket electronic telephone directories evolved into personal digital assistants. Chipmakers were releasingnew products at this time that were designed to transfer computing power from a desktop computer into mobilesmall computers that controlled gas pumps, cable television boxes, and an assortment of other appliances. J2ME is a reduced version of the Java API and Java Virtual Machine that is designed to operate within thesparse resources available in the new breed of embedded computers and microcomputers.Inside J2ME Consumers expect the same software and capabilities found on their desktop and laptop computers to beavailable on their cell phones and personal digital assistants. Developers seeking to build applications that run on cell phones, personal digital assistants, and variousconsumer and industrial appliances must strike a balance between a thick client and a thin client.Mobile Application DevelopmentPage 4

A thick client is front-end software that contains the logic to handle a sizable amount of data processing forthe system. A thin client is front-end software that depends on back-end software for much of the system processing. Processing on the wireless device might involve two steps: First the software performs a simple validationprocess to assure that all fields on the form contain information. Next the order is transmitted to the back-end system. The back-end system handles adjusting account balances and other steps involved in processing the order. A confirmation notice is returned by the back-end system to the wireless device, which displays theconfirmation notice on the screen. A key benefit of using J2ME is that J2ME is compatible with all Java-enabled devices. A Java-enabled deviceis any computer that runs the Java Virtual Machine.J2ME Architecture The modular design of the J2ME architecture enables an application to be scaled based on constraints of asmall computing device. J2ME architecture consists of layers located above the native operating system,collectively referred to as the Connected Limited Device Configuration (CLDC). The CLDC, which is installedon top of the operating system, forms the run-time environment for small computing devices. The J2MEarchitecture comprises three software layers (Figure 3-1). The first layer is the configuration layer that includesthe Java Virtual Machine (JVM), which directly interacts with the native operating system. The configurationlayer also handles interactions between the profile and the JVM. The second layer is the profile layer, whichconsists of the minimum set of application programming interfaces (APIs) for the small computing device. Thethird layer is the Mobile Information Device Profile (MIDP). The MIDP layer contains Java APIs for usernetwork connections, persistence storage, and the user interface. It also has access to CLDC libraries and MIDPlibraries. A small computing device has two components supplied by the original equipment manufacturer (OEM).These are classes and applications. OEM classes are used by the MIDP to access device-specific features suchas sending and receiving messages and accessing device-specific persistent data. OEM applications areprograms provided by the OEM, such as an address book.Run-Time Environment A MIDlet is defined with at least a single class that is derived from the javax .microedition.midlet.MIDletabstract class. Developers commonly bundle related MIDlets into a MIDlet suite, which is contained within thesame package and implemented simultaneously on a small computing device. All MIDlets within a MIDlet suiteare considered a group and must be installed and uninstalled as a group. Members of a MIDlet suite shareresources of the host environment and share the same instances of Java classes and run within the same JVM.This means if three MIDlets from the same MIDlet suite run the same class, only one instance of the class iscreated at a time in the Java Virtual Machine. A key benefit of the relationship among MIDlet suite members isthat they share the same data, including data in persistent storage such as user preferences. Sharing data among MIDlets exposes each MIDlet to data errors caused by concurrent read/write access todata. This risk is reduced by synchronization primitives on the MIDlet suite level that restrict access to volatiledata and persistent data. A MIDlet suite is installed, executed, and removed by the application manager runningon the device. The application manager also makes the Java archive (JAR) file and the Java applicationdescriptor (JAD) file available to members of the MIDlet suite.Inside the Java Archive File: All the files necessary to implement a MIDlet suite must be contained within a production package called aJava archive (JAR) file. These files include MIDlet classes, graphic images (if required by a MIDlet), and themanifest file. The manifest file contains a list of attributes and related definitions that are used by the applicationmanager to install the files contained in the JAR file onto the small computing device. Nine attributes aredefined in the manifest file; all but six of these attributes are optional.Mobile Application DevelopmentPage 5

The manifest file’s extension is changed to .mf when the MIDlet is prepared for deployment.MIDlet-Name: Best MIDletMIDlet-Version: 2.0MIDlet-Vendor: MyCompanyMIDlet-1: BestMIDlet, /images/BestMIDlet.png, Best.BestMIDletMicroEdition-Profile: MIDP-1.0MicroEdition-Configuration: CLDC-1.0 The MIDlet-n attribute can contain three values that describe the MIDlet. A comma separates each value. Thefirst value is the name of the MIDlet, which is BestMIDlet. Next is an optional value that specifies the icon thatwill be used with the MIDlet. In this example, BestMIDlet.png is the icon. The icon must be in the PNG imageformat. And the last value for the MIDlet-n attribute is the MIDlet class name, which is Best.BestMIDlet. Theapplication manager uses the class name to load the MIDlet.Inside the Java Application Descriptor File A JAD file is also used to provide the application manager with additional content information about the JARfile to determine whether the MIDlet suite can be implemented on the device. AJAD file is similar to a manifestin that both contain attributes that are name:value pairs. Name:value pairs can appear in any order within theJAD file. There are five required system attributes for a JAD nMIDlet-Jar-URL 18 A developer can include application attributes in a JAD file. An application attribute is a name:value pair thatcontains a value unique to the application.MIDlet Programming Programming a MIDlet is similar to creating a J2SE application in that you define a class and relatedmethods. A MIDlet is a class that extends the MIDlet class and is the interface between application statementsand the run-time environment, which is controlled by the application manager. A MIDlet class must containthree abstract methods that are called by the application manager to manage the life cycle of the MIDlet. Theseabstract methods are startApp(), pauseApp(), and destroyApp().The startApp() method is called by the applicationmanager when the MIDlet is started and containsstatements that are executed each time theapplication begins execution. The pauseApp()method is called before the application managertemporarily stops the MIDlet. The applicationmanager restarts the MIDlet by recalling thestartApp() method. The destroyApp() method iscalled prior to the termination of the MIDlet by theapplication manager.Mobile Application DevelopmentPage 6

public class BasicMIDletShell extends MIDlet { public void startApp() { } public void pauseApp() { } publicvoid destroyApp( boolean unconditional) { } } Both the startApp() and pauseApp() methods are public and have no return value nor parameter list. ThedestroyApp() method is also a public method without a return value. However, the destroyApp() method has aboolean parameter that is set to true if the termination of the MIDlet is unconditional, and false if the MIDlet canthrow a MIDletStateChangeException telling the application manager that the MIDlet does not want to bedestroyed just yet. At the center of every MIDlet are the MIDP API classes used by the MIDlet to interact withthe user and handle data management. The data-handling MIDP API classes enable the developer to performfour kinds of data routines: write and read persistent data, store data in data types, receive data from and senddata to a network, and interact with the small computing device’s input/output features.Event Handling A MIDlet is an event-based application. All routines executed in the MIDlet are invoked in response to anevent reported to the MIDlet by the application manager. The startApp() method in a typical MIDlet contains astatement that displays a screen of data and prompts the user to enter a selection from among one or moreoptions. A Command object is used to present a user with a selection of options to choose from when a screen isdisplayed. Each screen must have a CommandListener. A CommandListener monitors user events with a screenand causes the appropriate code to execute based on the current event.User Interfaces The design of a user interface for a MIDlet depends on the restrictions of a small computing device. A richuser interface contains the following elements, and a device with a minimal user interface has some subset ofthese elements as determined by the profile used for the device. A Form is the most commonly invoked userinterface element found in a MIDlet and is used to contain other user interface elements. Text is placed on aform as a StringItem, a List, a ChoiceGroup, and a Ticker. A StringItem contains text that appears on a form thatcannot be changed by the user. A List is an itemized options list from which the user can choose an option. AChoiceGroup is a related itemized options list. And a Ticker is text that is scrollable. A user enters informationinto a form by using the Choice element, TextBox, TextField, or DateField elements. The Choice elementreturns an option that the user selected. TextBox and TextField elements collect textual information from a userand enable the user to edit information that appears in these user interface elements. The DateField is similar toa TextBox and TextField except its contents are a date and time. An Alert is a special Form that is used to alertthe user that an error has occurred. An Alert is usually limited to a StringItem user interface element that definesthe nature of the error to the user.Device Data Small computing devices don’t have the resources necessary to run an onboard database management system(DBMS). A MIDlet can use an MIDP class—RecordStore—and two MIDP interfaces— RecordComparator andRecordFilter—to write and read persistent data. A RecordStore class contains methods used to write and readpersistent data in the form of a record. Persistent data is read from a RecordStore by using either theRecordComparator interface or the RecordFilter interface.J2ME Wireless ToolkitThe J2ME Wireless Toolkit is used to develop and test J2ME applications by selecting a few buttons from atoolbar.Building and Running a ProjectAfter downloading the J2ME Wireless Toolkit from the Sun web site, let’s create a new project by selecting theNew Project button from the toolbar. You’ll be prompted to enter a project name and class name. Enter HelloWorld as the project name and greeting.HelloWorld as the class name, which is the name of the first MIDlet thatis associated with the project. After selecting the Create Project button, the J2ME Wireless Toolkitautomatically creates a directory structure for the project and also creates the manifest file and JAD file.Mobile Application DevelopmentPage 7

You can see and modify attributes of these files by selecting the Settings option, which displays a dialog boxcontaining a series of tabs. The first tab displayed, Required (see Figure 3-9), contains a list of attributes that arenecessary for the manifest file and JAD 62 J2ME: The Complete Reference Complete Reference / J2ME: TCR /Keogh / 222710-9 / Chapter 3 file, as previously discussed in this chapter. The Optional tab (see Figure 3-10)contains attributes that are common to many projects but not required to build and deploy a J2ME application.Figure 3-9. List of required attributes Figure 3-8.Enter the project name and class name of the first MIDlet to begin the project. P:\010Comp\CompRef8\7109\ch03.vp Thursday, February 06, 2003 11:40:19 AM Color profile: Generic CMYK printer profile CompositeDefault screen Chapter 3: J2ME Architecture and Development Environment 63 Complete Reference / J2ME:TCR / Keogh / 222710-9 / Chapter 3 J2ME BASICS.The User Defined tab (Figure 3-11) containsoptional attributes specific to your application, asdiscussed previously in this chapter. This tab willbe empty until you select the Add button andinsert your own attributes.The MIDlets tab lists MIDlets of your project.Notice that the HelloWorld MIDlet is listed in thetab, which is the MIDlet you entered as the classname when beginning the project. A wellorganized file structure is automatically createdfor your project as a result of starting a newproject. Within the WTK104 directory, you’ll seean apps subdirectory in which the projects youcreate are stored. Browse the apps subdirectory tosee a subdirectory called Hello World, which isthe name that you gave to your project.A subdirectory of the apps directory is created for every project. And within the project’s subdirectory is anotherset of subdirectories. These are src, containing source code bin, containing the manifest.mf file, JAD file,and JAR file Figure 3-10. List of optional attributes P:\010Comp\CompRef8\710-9\ch03.vp Thursday, February06, 2003 11:40:20 AM Color profile: Generic CMYK printer profile Composite Default screen classes,containing the compiled classes tmpclasses, containing the preverify classes res, containing image, data, andother files required by the application.Hello World J2ME Style create the first MIDlet once the Java development kit, Connected Limited Device Configuration (CLDC),and Mobile Information Device Profile (MIDP)

Mobile phones have changed the way we live our lives providing voice calling, text messaging and mobile Internet access. The very first mobile phones were two-way radios that allowed taxi drivers and the emergency services to communicate. Motorola, on 3 April 1973 was first company to mass